From: | "Matt Clark" <matt(at)ymogen(dot)net> |
---|---|
To: | "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com> |
Cc: | <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: slow plan for min/max |
Date: | 2003-09-08 23:17:09 |
Message-ID: | LFEIJBEOKGPDHCEMDGNFEEGGCAAA.matt@ymogen.net |
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Thread: | |
Lists: | pgsql-performance |
>This is a Frequently asked question about something that isn't likely to
>change any time soon.
You're right, it is in the FAQ, but pretty well buried. It is entirely
non-obvious to most people that min() and max() don't/can't use indices.
Something so counterintuitive should be explicitly and prominently
advertised, especially since the "order by X limit 1" workaround is so
simple.
Actually, referring down to later parts of this thread, why can't this
optimisation be performed internally for built-in types? I understand the
issue with aggregates over user-defined types, but surely optimising max()
for int4, text, etc is safe and easy?
Of course I may be so far out of my depth as to be drowning, in which case
please put me out of my misery.
M
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